Counting circuit



April 24, 1956 D. SAYRE COUNTING CIRCUIT Filed Dec. 29, 1952 B WWW l/VVENTU/F DAVID SAYRE ATTORNEYS David Sayre, Philadelphia, Pa;,

United States Patent-O 2,743,359 I I GOUNTING cincuir' v a'ssignor,- b'y 'mesne-assignments; tothe "United" States of America as'represent'ed by the Secretaryof 'the'Navy- Application. December. 2 9, 1952, Serial :No. 328,397 1 2 Claims: (Cli '250:* -2'7) This application is a continuation-impart. of' my copending application, Seria-LNo; 635;095, filedDecember 14, 1945, for Counting Circuit, now abandoned.-

This invention relates to electronic control I circuits. and more particularly to a"1P].l'1S6"COI1I1i6l' incorporating a cathode follower to provide: a distinct and dependable voltage step when: triggered. Heretofore. pulsecounters were limited in application'beoausewthey operated 'satisr faetorily. only when: the applied pulses werev of unifo'rm size and shape. Furthermore, they; tended. to:be unstable in their operation.

Thisiinvention contemplates=theuse of a cathoderfollower in which a triode is biased so that the cathode potential isnormallyat almor'e positive value thanv the control grid, and further that the control gridof the cathode follower is isolated, from thev cathode thereof by means of twosequentiallyoperating electronic switches. The input .pulses to be counted are applied. directly to the first electronic switch and through a=time delay circuit to the second electronic switch to transfer thecathode potential of the cathode follower to the control grid thereof in twosuccessive steps while maintaining the controlgrid isolatedfrom' the cathode; A-.stepped in creas'e ofvoltage'at-both the control grid and the cathode results in response. to eachinput pulse to be-counted.

The inventionfurther contemplates: an electron tube circuitresponsive to a predetermined amplitude of cath ode follower oathode'p'otential'to. :develop a single output pulse for alpredetermined number" of input'pulses and a circuit' for coupling-the output .pulse to the/control grid of the cathode followers to: restore. potential conditions at both control grid and cathoderw aninitiallfixedireference level. V

A primary'objectofs-the present invention is to eliminate. the foregoing. difiiculties'; in: pulse counters.

Another andmoreisp'ecifie object of the'invention-is to provide a pulse-counter. incorporating the useof. a

cathode follower to-provide a? dependable. voltagestep wave form upon the application of pulses thereto.

Another object of-the invention is to provide means ofcounting pulses. whichmaynot -be of uniform size and sha e.

ther objects. and many of the attendant advantages of this invention will.be readily appreciated as the same becomes better understood by. reference to the following detailed description when considered in connection with the accompanying drawingwhich is'a circuit diagram of an embodiment of the invention:

Referring to the drawing, a triode 31 is connected as a cathode follower circuit in which the plate is connected directly tothe positive terminal 37 of a direct-current energy source- The cathode'15 oftriodeSl is connected to ground'through the cathode follower load resistance 17. The operating conditions: of triode 31- are'selected so that'triode 31:isconducting whenthe grid 16 of triode 31 is at ground potential, the-initial reference. grid potem tial level for: the count; Aismall: positive. voltage. appears acrosslcathode'i follower load, resistor 17 as a result of.

2,743,359 Patented Apr. 24, 1956 t 2 spacecurrent of triode 31'; which places cathode-15* of mode 31- at a positive: potential with respect to grid 16.

An incoming :positive :pulse applied. at terminal 10 rendersvconductive anielectronic'switch, here shown as a normally-- nonconductingtwo-way: double triode clamping circuitll', the operationaofiwhich will'be discussed more fully hereinafter. For: a time substantially. equal to the pulse duration,. clamping circuit 11: connects capacitor 12.to the cathode :15 =of1cathode; fbllower 31 thereby bringing capacitor 12 to substantially the same voltage-as the cathode.

The two way double triode clamping circuit 11 is a conventional clamping circuit arranged so. that a: negativebias is appliedfrom D: C. source: 35; for example a battery, through..resistor"34, to the control=grids to maintain triodes .32 and =331normally nonconducting. A positive signal or. pulse. applied through coupling cap'acitor 36=to the control fgrids 'o'f triodes32 and 33 makes itrpossible for triode 32 to become conducting in 'the event that thepoten'tia'l' at' cathode 15: is more positive than the potential existing o'n capacitor 12. By conduction: of triode 32: the potential. on capacitor 12 is made substantially equal that of cathode 15. On the other hand; in the event that the potential on capacitor 12 should become-more positive'than th'e potential at cathode 15, triode 33 is renderedconducting and capacitor 12- is dischargedthrough triode 33 and resistor 'i i to substantially the same potential asthat= appearing at cathode 15. As is'wellknown in the art triodes having a low plate re-' sistance are selected inorder thatthe voltage drop across theclampin'g'triode shall be a minimum.

Aninco'ming inputpulse'applied at terminal ltl is also applied to delay 'line 14 (a suitable time delay circuit-may be used) so that a short time later the same positive'incoming pulse first applied to clamping circuit ll-is applied to the normally nonconducting two-way doubletriode clamping circuit Iii-which behaves in the same manner as that'described for clamping circuit 11 For the ti'm'e duration ofthe-delayedpulse, circuit 15 acts to :close the circuitbetween capacitor 12 and capacitor 12a which is also connected to :the grid 16-of cathode-follower 31. It will be understood that delay line 14 provides a delay less than the time intervalbetw'een incoming pulses-but of sufficient time so that the clampingcireuit 1 1' is 'no'nconducting atthe time when-clamping circuit 13 is biased to-conduction onenergized by the delayed pulse. 'This condition of operation makes it impossible for the cathode follower grid 16-to be connect-ed directly to its cathode 15. Assuming that the grid 16 of cathode follower fii is initially at ground potential, it-is seen that the positive potential appearingacross cathode follower"load-resistor 17 is transferred to capacitor 12 through the operation ofclamping circuit 11 and subsequently is transferred through clamping circuit 13to capacitor 12a thereby: raising the potential of grid 16 by a definite positive voltage step. This increase in grid voltage causes the cathode follower 31 to conduct more heavily, thereby. increasing the current flow through load resistor 17, thereby raising the potential 'on cathode 15 by a definite positive step. However, this higher cathode potential cannot applied at terminal 'ltl'again acts to transfer the potential of cathode 15 to capacitor 12 and subsequently, by the time delay of circuit 14, from capacitor 12 to capacitor 12a again to increase the potential of .grid'loby a definite positive step. In this manner a staircase or rising and stepped voltage wave form is generated both at the grid 16 and the cathode 15 of cathode follower 31 by a series of incoming pulses.

The cathode of cathode follower 31 is directly connected to the control grid of a thyratron 18 or similar trigger tube, having the anode 19 thereof returned to a positive power supply 38 through a load resistor 22. The thyratron 18 is rendered normally nonconductive by a positive potential applied to the cathode 27 by the connection thereof to the junction between resistors 24 and 25 forming a voltage divider across the cathode follower anode positive supply 37 and ground. The capacitor 26 is used to stabilize the potential across resistor 25, used to bias the thyratron.

On the voltage step which carries the cathode 15 above a certain voltage the thyratron 18 fires. The resulting current flow through the load resistor 22 causes the voltage on the anode 19 to drop to a value low enough to cut 01f the current flow in the thyratron 18. This rapid rise and fall of current produces a negative voltage pulse at anode 19 which is coupled to an external circuit through capacitor 20. Simultaneously, this negative voltage pulse appearing at anode 19 is applied by means of capacitor 21 to restore the voltages of the grid 16 and cathode 15 to the initial reference potential level. The diode 23 connected between control grid 16 and ground acts as a diode clamping circuit to prevent the grid 16 from being returned to a potential lower than ground when the thy- V ratron fires, thereby establishing the aforesaid initial reference grid potential at ground potential.

It will be noted that the duration of the signal pulses to be counted must be long enough to permit complete charging of capacitors 12 and 12a. Likewise, it is necessary that the voltage difference between the control grid and the cathode of cathode follower 31 shall be a step of sufiicient amplitude to permit positive firing of the thyratron at the desired count and to prevent firing of the thyratron at a lower count. It is also to be noted that in normal operaion the last input pulse of a counting sequence shall have a duration time so that the time of conduction of clamping circuit 13 is not only long enough for the potential on capacitor 12a and control grid 16 to increase the potential of cathode 15 to cause thyratron 18 to fire, but also the time of conduction of clamping circuit 13 is long enough to permit discharge of capacitor 12 as well as capacitor 12a to ground potential. However, if through abnormal conditions, these capacitors are incompletely discharged by the pulse applied through capacitor 21, the first incoming pulse in a new sequence applied at terminal acts, for example, to render triode 33 conducting and reduces potential on capacitor 12 by discharge through triode 33 and cathode follower load resistor 17 to produce a substantial equality of potential at cathode and capacitor 12. V

In this manner output pulses coupled through capacitor are developed at some submultiple of the applied pulses as determined by the thyratron cathode bias. The advantages of the invention are very good stability and ability to handle fast counting rates. Furthermore, the input pulses need not be of a uniform size or shape to generate the proper staircase wave forms.

I claim:

1. Electrical apparatus for providing an output pulse when energized by a predetermined number of input pulses, comprising a cathode follower circuit including an electron tube having at least a cathode, a control grid and an anode wherein the input signal is applied between said control grid and ground and the output signal is taken from said cathode and ground, means energized by an input pulse for raising the input potential of said cathode follower, thereby raising the potential of said cathode follower output, an electron tube biased to be normally nonconductive, said electron tube being coupled to the output of said cathode follower for producing said output pulse in response to a rise in potential of said output to a predetermined value to provide said output pulse, and

4 means responsive to said output pulse to reduce said input potential.

2. Electrical apparatus for providing an output pulse when energized by a predetermined number of input pulses, comprising a cathode follower including an electron tube having at least a cathode, a control grid, and an anode, said cathode follower having a cathode load resistance, a first clamping circuit connected between said cathode load resistance and a second clamping circuit, a delay line, means for applying said input pulses simultaneously to said first clamping circuit and said delay line, said second clamping circuit being connected between said control grid of said cathode follower and said first clamping circuit, said second clamping circuit being energized through said delay line, an electron tube biased to be normally nonconductive and biased by said cathode follower load resistance to be operative at a predetermined potential to produce said output pulse, and means applying said output pulse to reduce the potential of said cathode follower control grid.

3. Electrical apparatus for providing an output pulse when energized by a predetermined number of input pulses, comprising a cathode follower including an electron tube having at least a cathode, a control grid and an anode, said cathode follower having a cathode load resistance, a first electron switch connected between said cathode load resistance and a second electronic switch, a delay line, means for applying said input pulses simultaneously to said first electronic switch and said delay line, said second electronic switch being connected between said control grid of said cathode follower and said first electronic switch, said second electronic switch being energized through said delay line, an electron tube biased by said cathode follower load resistance to be operative at a predetermined potential to produce said output pulse, and means operative in response to said output pulse to restore the potential of said cathode follower control grid to its initial amplitude.

4. An electrical counting circuit for providing an output pulse when energized by a predetermined number of input pulses, comprising a cathode follower circuit including an electron tube having at least a cathode, a control grid and an anode wherein the input signal is applied between said control grid and ground and the output signal is taken from said cathode and ground, means actuated by said input pulses for producing a stepped voltage wave form, wherein each of said input pulses is represented by one of said voltage steps, means applying said stepped voltage wave form to the input of said cathode follower circuit to produce a stepped voltage output from said cathode follower circuit, an electron tube circuit biased to nonconduction and responsive to a predetermined amplitude of said cathode follower circuit stepped output voltage to produce said output pulse, and means responsive to said output pulse to restore said cathode follower circuit input to its initial amplitude.

5. A counting circuit for counting pulses of varying wave forms and amplitudes, comprising a cathode follower circuit, a reference capacitor, a delay line, means responsive to each input pulse to connect said reference capacitor to the output of said cathode follower circuit for the time duration of said pulse, means applying said input pulse to said delay line to produce a secondary pulse delayed in time with respect to said input pulse, means responsive to said secondary pulse to connect the input of said cathode follower circuit to said reference capacitor for the time duration of said secondary pulse, thereby changing the amplitude of the potential of said cathode follower input by a step equal in amplitude to the difference between said cathode follower output and input potentials and hence changing said cathode follower output potential by a like amount, means operative when said cathode follower output potential reaches a predetermined amplitude to produce an output pulse, and means responsive to said output pulse to restore said cathode follower input potential to its initial amplitude.

6. A counting circuit for counting pulses of varying wave forms and amplitudes comprising, a cathode follower circuit, a reference capacitor, a delay line, an electronic switch responsive to each input pulse to connect said reference capacitor to the output of said cathode follower circuit for the time duration of said pulse, means applying said input pulse to said delay line to produce a secondary pulse delayed in time with respect to said input pulse for a period longer than the time duration of said input pulse, a second electronic switch responsive to said secondary pulse to connect the input of said cathode follower circuit to said reference capacitor for the time duration of said secondary pulse thereby changing the amplitude of the potential of said cathode follower input by a step equal in amplitude to the difference between said cathode follower output and input potentials and hence changing said cathode follower output potential by a like amount, an electron tube biased to be nonconducting and responsive to a predetermined amplitude of said cathode follower circuit stepped output voltage to produce an output pulse, and means applying said output pulse to reduce said cathode follower input potential to its initial amplitude.

7. An electrical counting circuit for providing an output pulse when energized by a predetermined number of input pulses comprising, a cathode follower circuit ineluding an electron tube having at least a cathode, a

control grid and an anode, first and second electronic switches connected between said cathode and grid, a time delay circuit, means for applying said input pulses directly to said first electronic switch and through said time delay circuit to said second electronic switch whereby the cathode potential of the cathode follower is transferred to the grid of said cathode follower to change the potential of said grid by a step equal in amplitude to the diiference between said cathode follower grid and cathode potentials, means responsive to said cathode follower cathode potential at a predetermined amplitude for producing an output pulse, and means for coupling said output pulse to said grid to restore said grid potential to its initial amplitude.

8. Apparatus as in claim 4 in which said last-mentioned means includes a diode connected between said cathode follower control grid and ground to limit the reduction of grid potential to ground potential.

9. Apparatus as in claim 5 in which said last-mentioned means includes a diode connected between said cathode follower control grid and ground to limit the reduction of grid potential to ground potential.

10. Apparatus as in claim 6 in which said last-mentioned means includes a diode connected between said cathode follower control grid and ground to limit the reduction of grid potential to ground potential.

11. Apparatus as in claim 7 in which said last-mentioned means includes a diode connected between said cathode follower control grid and ground to limit the reduction of grid potential to ground potential.

12. An electrical counting circuit for providing an output pulse when energized by a predetermined number of input pulses comprising, a cathode follower having a load impedance in its cathode circuit, a first capacitor connected in the grid circuit of said cathode follower, a second capacitor, a normally open switch for connecting said second capacitor across said load impedance in response to an input pulse, means for applying the potential of said second capacitor to said first capacitor before the arrival of the next input pulse and ate time when said switch is open, and means connected to the output of said cathode follower adapted to produce an output pulse in response to a predetermined amplitude output of said cathode follower.

References Cited in the file of this patent UNITED STATES PATENTS 2,413,440 

